This invention relates to dock loading equipment and in particular, dock levelers used to bridge the space between a vehicle and a dock surface. Specifically, this invention deals with vertically storing dock levellers and a lock system to secure such devices.
Dock levelers are well known as typified by a number of commercial devices such as the Serco W Series leveler. Such devices are employed at docks to provide a technique for loading and unloading equipment such as fork-lift trucks to move freely from the dock surface to and from the vehicle. Levelers, commonly known as dock boards are hinged for movement to compensate for the variation in height between the vehicle bed and the dock surface. They are conventionally provided with a lip that is actuated in conjunction with the dock board which spans the gap between the dock edge and the rear of the truck.
Dock levelers may store either vertically or horizontally. Horizontally stored dock levelers are generally mounted in pits cut into the dock. The leveler, when stored, is positioned with its surface flush with the dock to establish a so called "crosstraffic" position that allows movement transverse to the dock. In this storage position, the lip usually hangs pendent closing the pit. Such horizontally storing levelers, while in common usage, have a number of disadvantages. In operation, a truck must stop and have the rear doors opened prior to finally parking against the dock. This is necessary since typical dock heights and door openings block the trailer doors from opening when the truck has fully backed into position. When the truck resumes backing in, cargo may spill out, damaging freight.
Additionally, the dock area is a collection point for debris accumulating in the pit underneath the dock leveler. Frequent cleaning is required and in extreme cases, the operation of the leveler may be impaired. Security is also a problem with conventional horizontally storing levelers. Intruders and rodents enter the dock area by going under the door through the dock leveler.
These disadvantages have lead to the consideration of vertically storing dock levelers. Such devices perform the same function, providing an access bridge between the dock and the vehicle, but are positioned inside the dock area on the dock surface. Such devices are not mounted in any pit. They are stored vertically at a point inside the dock to allow dock doors to close and completely seal the dock. A vertically storing dock leveler may be either hydraulically or electrically actuated by a control panel located near the dock board. The dock board is lowered into position by such an actuator with the lip actuated either manually or hydraulically. When stored in the vertical position, customarily a solenoid is used in the power actuation circuit so that when the power to the leveler is turned off, the leveler is locked in its present position.
Given the need for increased safety in the dock environment, additional means are needed to insure that a vertically storing dock leveler will not be accidentally lowered by a worker. For example, given the noise level at a dock, one person could mistakenly lower a leveler or lower the wrong leveler in a situation where multiple devices are operated from a common control panel. There is also the problem of damage to the actuation system that could allow the lift system to release the leveler from its locked position. Thus, a need exists for a lock system independent of the actuation mechanism to provide adequate security and safety for a vertically storing leveler.